As evidenced by the following examples, there have been numerous prior attempts over many years to provide externally applied safety devices for firearms.
U.S. Pat. No. 3,018,576 to Riechers discloses a block form locking device that clamps over the side ejection port of a tubular magazine shot gun. The device is substantially entirely external of the firearm, does not inhibit loading or unloading of the magazine and employs rubber gasketing on external contact surfaces making the unit vulnerable to unauthorized removal by a prying action.
U.S. Pat. No. 3,605,311 to Hermann discloses a locking device for tubular magazine firearms that is inserted in and fully occupies, the breech area behind the chamber of the barrel. The device does not restrict access to the magazine, is not readily adaptable to bottom ejection port type firearms and locks the gun in the open position, thus adversely affecting the utility for sales display or handling demonstrations.
U.S. Pat. No. 4,058,923 to Smith discloses a snap fitting type of clip for a tubular magazine shot gun which is largely exterior of the firearm. There is no disclosure or suggestion of a locking feature.
U.S. Pat. No. 4,654,992, to Lavergne discloses an exterior locking device for tubular magazine firearms that provides a bar extending across the bottom loading port and a tab projecting into the side ejection port that restricts movement of the breech block to the rear two thirds of its normal travel. The employment of this device makes the finish of the firearm vulnerable to damage caused by forceful closing of the breechblock, while the device is not readily adaptable to bottom ejection port type firearms and may be prone to unauthorized removal by prying.